Various methods exist to remove calculi from body cavities. Calculi, such as those formed in a gall bladder or kidney, can cause significant problems for a patient. For example, ureteral constriction and blockage can cause hydronepherosis, a condition characterized by the damming of urine in the kidneys. A frequent blockage site is the junction of the ureter and the renal pelvis. Acquired blockages are most commonly caused by kidney stones that root themselves in the ureteral lumen wall.
Often, kidney stone removal is performed using stone retrieval devices based on wire baskets, lithotrypsies, pharmaceutical therapeutics or surgery. For example, a cystoscope can be introduced into the ureter to remove an embedded stone. The cytoscope typically includes a wire basket disposed at the distal end. The stone is trapped in the basket, and the cystoscope and trapped stone are then removed from the body.
Existing methods have several deficiencies. These treatments can be difficult to perform, can lead to severe adverse events, and can entail high cost. For example, a retrieval basket can have difficulty trapping calculi of some sizes or shapes. Body tissues can be damaged while spreading the basket and attempting to grasp a stone. A basket may have difficulty grasping a stone that is embedded in a wall of a body lumen. Further, the size of the basket/stone combination may create difficulty in removing the apparatus from the body. Use of ultrasound or solvents can damage body tissues in the vicinity of the stone.